In 1842, Charles Dickens embarked on a five-month trip through the United States that would take him through the cities of the northeast and then west to the frontier. After arriving in the States, Dickens told his hosts that "the Falls of Niagara and your Penitentiary are two objects I might almost say I most wish to see."

Dickens wasn't the first European intellectual who had crossed the Atlantic to visit Eastern State Penitentiary. A decade earlier, Alexis de Tocqueville had been sent by the French government to study the Philadelphia prison. At the time, it was one of the country's biggest attractions. In 1858, 10,000 tourists purchased tickets from the warden's office and took a tour. Around the same time, the Rihouet porcelain factory in Paris produced a dessert plate featuring a painting of the prison's neo-Gothic façade.

What drew the attention of Americans and Europeans was an innovative method of punishment being pioneered at the prison called solitary confinement. While the practice had roots in medieval monasteries, where it was used to punish disobedient monks, solitary confinement came to prominence as a form of criminal punishment in the United States soon after the Revolution.

One of the most prominent advocates for this new type of punishment was Dr. Benjamin Rush of Philadelphia. He was a signatory of the Declaration of Independence and was widely regarded as America's foremost physician. Soon after the Revolution, Rush, who was also a social critic and an activist, took on the task of crafting a criminal justice system fit for a democratic republic.

In colonial America, capital punishment had been common, and not just for murderburglary and sodomy could earn an offender the death penalty as well. For less serious offenses, criminals were generally subjected to physical punishments meted out on the public square. In a frontier nation of small towns, public embarrassment was seen as the key to deterring crime. Physical punishment, whether in the form of the stockade or the whipping post, was combined with the psychological punishment of being shamed in front of the community. Jails existed, but they were used mainly to hold criminals before trial and punishment. There were no cells and few rules: Men and women were housed together, and alcohol was often available.

Rush objected to capital punishment, corporal punishment, and America's unruly jails, and he published diatribes against all three. Capital punishment, in Rush's opinion, reeked of monarchical tyranny. "An execution in a republic," he wrote, "is like a human sacrifice in religion."

In 1787, at a soiree held in Benjamin Franklin's living room, Rush presented an essay titled, "An Enquiry Into the Effects of Public Punishments Upon Criminals, and Upon Society." Rush declared that "crimes should be punished in private, or not punished at all." He claimed that public punishment failed to rehabilitate the criminal and risked letting the convict become an object of community sympathy. In lieu of public, physical punishments, Rush endorsed the creation of a "house of repentance." Grounded in the Quaker principle that each individual is blessed with "Inner Light," Rush envisioned a place of anonymity, solitude, and silence, where prisoners could dwell on their crimes, repent, and return rehabilitated into society. "A whipping post, nay even a gibbet are all light punishments compared with letting a man's conscience loose upon him in solitude," he wrote.

In the months following Franklin's salon, Rush and other reformers mobilized to put their ideas into practice, forming the Philadelphia Society for Alleviating the Miseries of Public Prisons to lobby the legislature to reform the prison system. Rush was chosen by members of the society to visit the city's jails and report on the health of prisoners. As the physician in charge of "maniacal patients" at Pennsylvania Hospital, Rush had experience monitoring people being held against their will. He would later write America's first psychiatry textbook, Medical Inquiries and Observations Upon the Diseases of the Mind, in which he argued that mental illness was caused by a malfunctioning of blood vessels in the brain. His proposed treatment was bloodletting.

In 1821, the reformers finally convinced the Pennsylvania legislature to approve funding for Eastern State Penitentiary, which would be the largest public building in the country; with a price tag of nearly $800,000, it was likely the most costly one as well. No expense was spared: To prevent disease, each cell in the new prison was equipped with a toilet, a rare luxury at the time. When the penitentiary opened in 1829, President Andrew Jackson was still using an outhouse on the White House lawn.

The principles of the penitentiary systemsilence, solitude, surveillance, and anonymitywere incorporated into the architectural plan. Eastern State was designed by John Haviland, a young architect, who proposed a hub-and-spokes model that allowed for constant surveillance. Inmates were housed in 8-by-12-foot cells arranged along a series of cellblocks radiating out from a central observation tower.

Each prisoner remained in his cell at all times, save for a brief daily exercise period held in an individual pen adjoining each cell. Prisoners ate their meals in their cells and did small-scale prison labor there like shoemaking. On the rare occasions when prisoners were allowed to leave their cells, they were prevented from interacting with other prisoners by hoods they were forced to wear to protect their anonymity. They were also forced to use numbers instead of names for the same reason. Silence was maintained at all times in the prison, and reading the Bible was the only activity other than labor that was permitted. Reformers believed that cutting inmates off from the world would foster meditation that would lead to rehabilitation, so visits from family or friends were prohibited. On average, inmates spent two to four years alone in their cells, underneath a single round skylight, known in the prison as the "eye of God."

The expense of the building limited its influence in the United States, but Eastern State was widely copied in Europe and even in Latin America and Japan, where economic conditions made the model more attractive. Over 300 prisons were built on Eastern States' hub-and-spokes model, in cities as diverse as London, Paris, Milan, St. Petersburg, and Beijing. Architectural historians consider the hub-and-spokes penitentiary to be the only American building type to have had global influence until the first skyscrapers began to rise in Chicago and New York in the 1880s.

At the cornerstone-laying ceremony for Eastern State in May 1823, the Philadelphia philanthropist Roberts Vaux told the crowd that Pennsylvania was proudly pioneering a new penal system that substituted "milder correctives" for "those cruel and vindictive penalties which are in use in the European countries."

Not all Europeans were convinced. In 1826, the Revolutionary War hero Marquis de Lafayette visited Eastern State, then under construction. He had spent three years in solitary confinement as a prisoner of war, and was aghast. Lafayette reportedly told a friend back in Paris, "Of all the sufferings of my life, none have exceedednone have equaled that single oppression of being, for three whole years, asleep and awake, sitting and standing, exposed to the view of two eyes, watching my every motion, taking from my very thoughts every idea of privacy."

When Alexis de Tocqueville arrived in Philadelphia in 1831, he requested permission to interview inmates at the newly opened prison. His interviews are some of the earliest documents to shed light on the psychological effects of the penitentiary's solitary system. A well-educated inmate imprisoned for bankruptcy fraud told Tocqueville that he was "often visited by strange visions. During several nights in succession, I saw, among other things, an eagle perching at the foot of my bed." Another inmate told Tocqueville that his soul was "sick"; two others were so disturbed that they couldn't speak coherently.

Even without a modern understanding of the human psyche, there were observers who saw that the solitary system was driving inmates insane. Despite his access to prisoners, the usually perceptive Tocqueville wasn't one of them. Of the disturbed prisoners he wrote credulously, "The warden of the prison has assured us that they arrived in this state at the prison."

Dickens, who also interviewed prisoners at Eastern State, was far more skeptical. In his travelogue, American Notes, he described Philadelphia's system of "rigid, strict, and hopeless solitary confinement" as "cruel and wrong." But while he objected to the system, he did not question the motives of the prison reformers who conceived of it. "In its intention, I am well convinced that it is kind, humane, and meant for reformation; but I am persuaded that those who devised this system of Prison Discipline, and those benevolent gentlemen who carry it into execution, do not know what it is that they are doing."

Dickens didn't accept that the penitentiary represented human progress over the days of floggings on the public square, or as his prose suggested, even the medieval torture chamber. "I hold this slow and daily tampering with the mysteries of the brain to be immeasurably worse than any torture of the body." After interviewing a man who was two years into a five-year sentence for larceny, Dickens, one of the world's greatest chroniclers of human degradation, wrote, "I never saw or heard of any kind of misery that impressed me more than the wretchedness of this man."

Officials at Eastern State maintained that their system was the best yet devised, and elite opinion in the United States was firmly behind the idea of solitary confinement. The debates of the day focused largely on whether the system at Eastern State was cost effective when compared with New York's penal system. In New York, at the Auburn prison near Syracuse and later at Sing Sing in Westchester County, a modified system of solitary confinement was being put into practice. While inmates spent their nights in solitary cells, they worked together silently in a common area during the day. This allowed wardens to set up profitable prison industries that could offset the costs of prison construction. According to the Columbia University historian David Rothman, "If the literature on Auburn versus Pennsylvania never quite matched the outpouring of material on the pros and cons of slavery, it came remarkably close."

In the 1858 annual report about Eastern State, officials claimed that the prison actually made inmates saner. According to statistics prepared by the prison physician, 26 prisoners or 4.86 percent of the total population experienced "mental improvement" after being incarcerated in the penitentiary. When inmates did suffer breakdowns, their mental illness was often blamed on "self-abuse"masturbationwidely believed at the time to drive men insane. The arrogance of the system can be heard in the annual report of 1869, which lists the arguments against the solitary system, refutes them, and concludes, "We are justified in unequivocally asserting that the Pennsylvania system of penitentiary discipline understood and properly applied, is not injurious to the health, has no injurious influence on the mind, is neither inhuman nor cruel ... and that if properly administered, it is now the most philosophic and effective system for the treatment of crime as an actual condition of persons in all societies."

Despite this vehement defense of the solitary system, in the period after the Civil War, the regimen at Eastern State was slowly abandoned. Historians have theorized that the rise in foreign immigrants among the prison population decreased public sympathy for prisoners and made expensive penal reform less politically popular during the postwar period. Without enough funding to keep the system running, inmates were frequently doubled up in cells. In 1913, the solitary system was officially abandoned. Solitary confinement became a short-term punishment for misbehaving prisoners rather than the prison's standard operating procedure.

Eastern State closed in 1970, five years after it had been declared a National Historic Landmark. In 1994, Eastern State was again opened to tourists, this time as a history museum. As Eastern State was being converted into a museum, the United States was on a prison-building binge: More than half of all U.S. prisons in use today were built in the past 25 years, to house a prison population that has risen almost 500 percent over roughly the same period. The United States has the highest incarceration rate in the world. In raw numbers, it has more prisoners than China, a country with over four times as many people.

In the wake of the urban riots of the late 1960s, conservative politicians began winning elections with calls for a return to "law and order." The movement dovetailed with a call from the left for less judicial discretion in sentencing, as liberals believed that judges were using their discretion to sentence minority defendants to longer terms than whites. In 1973, New York State passed the Rockefeller drug laws, establishing mandatory minimum sentences for drug crimes, and other states soon followed suit. At the federal level, Senators Strom Thurmond, the Republican from South Carolina, and Ted Kennedy, the Democrat from Massachusetts, collaborated on a bill that limited judicial discretion.

"Tough on crime" politicians translated their rhetoric into action, building more prisons and limiting programs aimed at rehabilitation, like educational programs. Even with the prison-building boom, prison overcrowding became a pressing problem. As rehabilitation programs shrank, overcrowded prisons began to spawn more violent outbursts, and conflict between prison gangs grew.

In 1983, violence swept the federal penitentiary at Marion, Ill. Two guards were stabbed to death, and guards murdered one inmate and attacked others. In response, Marion was "locked down": Prisoners were forced to stay in their cells for 23 hours a day. The experiment in long-term solitary confinement at Marion worked. Violence stopped and disruptions were rare. By accident, the modern supermax prison had been invented.

Supermax prisonshigh-tech, maximum-security facilitieswere the answer politicians and corrections departments were looking for to solve the problem of increasing violence in prisons. Following Marion's lead, corrections departments around the country began building supermax prisons, or adding supermax wings to their existing prisons to handle the growing number of violent prisoners who could not be controlled in the traditional prison system. Today there are 20,000 supermax inmates in the United States, roughly 2 percent of the total prison population, though in some states the proportion is much higher: In Mississippi, 12 percent of prisoners live in supermax units.

The system of punishment in supermax units resembles nothing so much as the system of punishment pioneered at Eastern State. The Pelican Bay Security Housing Unit, which cost California taxpayers a quarter of a billion dollars, is perhaps the most notorious supermax. From the air it looks like a high-tech version of the Philadelphia prison: Its hub-and-spokes design is clearly descended from John Haviland's 19th-century architectural plan. Inmates in the SHU (known as "the shoe") are kept in their cells close to 24 hours a day. As at Eastern State, inmates eat in their cells and exercise in isolated attached yards.

Economic imperatives still dictate prison philosophy, and Pelican Bay inmates are frequently doubled up to save money. Family and friends are allowed to visit, but since the majority of Pelican Bay prisoners are from southern California, visits are infrequentPelican Bay sits near the Oregon border, as far from San Diego as Chicago is from New York. The Pelican Bay SHU houses prisoners who are not easily handled in the prison system, and those who are uncontrollable in the SHU stay in the SHU, often for years on end.

Dr. Stuart Grassian, a Harvard Medical School psychiatrist who was given access to SHU inmates to prepare for providing expert testimony in lawsuits against the California Department of Corrections, has concluded that the regimen in security housing units drives prisoners insane, and he estimates that one-third of all SHU inmates are psychotic. He writes of what he calls "the SHU syndrome," the symptoms of which include self-mutilation and throwing excrement.

Dr. Terry Kupers, a psychiatrist who has interviewed supermax inmates, writes that a majority of inmates "talk about their inability to concentrate, their heightened anxiety, their intermittent disorientation and confusion, their experience of unreality, and their tendency to strike out at the nearest person when they reach their 'breaking point.' " Even those inmates who don't become psychotic experience many of these symptoms. Those least likely to become mentally ill in solitary confinement are prisoners who can read, because reading prevents the boredom that can lead to insanity. (The human psyche appears not to have changed since the days of Eastern State, when an inmate told Alexis de Tocqueville that reading the Bible was his "greatest consolation.") Because roughly 40 percent of U.S. prisoners are functionally illiterate, however, reading can provide solace and sanity to only a fraction of those behind bars.

Forty-one states have supermax units that resemble Pelican Bay. But while experts agree that long-term solitary confinement drives prisoners insane, there are no international luminaries flocking to see American prisons today. Even if they did, it's not clear what they would be permitted to learn. On their visits to America, Dickens and Tocqueville were encouraged to interview Eastern State prisoners in their cells. Today, a number of states bar members of the media from interviewing prisoners. Among them are California and Pennsylvania.

Daniel Brook is a staff writer at The Philadelphia City Paper. His work has also appeared in Harper's and Mother Jones.